Shock absorbing or damping snubbers are widely used in electric power plants, particularly plants employing nuclear energy, in which pipes are yieldably attached, by way of pipe hangers or supports, to plant structure. In such applications, the snubbers are operatively connected, usually as part of a strut assembly, between the pipe and structure. The snubber's function is to permit free motion or movement of the pipe relative to the structure in response to slow thermal expansion or contraction of the pipe, but to resist or damp rapid relative motion of the pipe, such as might be induced by seismic shock or vibration.
While the life of a high quality snubber should be of the order of several decades, their function is so important to the safe operation of the electrical generating plants that present practice requires that such snubbers be subjected to periodic test to ensure that they will operate properly. Accordingly, the practice in the industry is to have technicians, who may have to be protected from the radiation encountered in the area, to remove the snubber, or the snubber and strut assembly, bodily from the system. Then the snubber is decontaminated to ensure that radiation therefrom, induced by the environment from which it was taken, is reduced to a level low enough to permit handling by others. Thereafter, the snubber is transported to a test location for examination and test by test personnel. Following test, if the snubber is determined to operate within a desired specification, the snubber is replaced in the system. If the snubber is not performing properly, it must be replaced, or repaired prior to reinstallation.
With large snubbers and snubber and strut assemblies weighing hundreds of pounds, and with some plants employing hundreds of snubbers, it is evident that such test procedures are highly cumbersome, time-consuming, and expensive to perform. It has been estimated that for each one million dollars invested in snubbers, a nucelar power plant may spend, over the life of the snubbers, three times that amount or more in performing the required periodic tests in addition to the cost of repairs.
The above-enumerated problems involved in current snubber test practices are overcome, according to the present invention, by providing an improved snubber that lends itself to in situ test procedures and, further, by providing a method and apparatus for testing such snubbers in their normal, operational location in the snubber system. The test may be performed reliably, quickly, safely and inexpensively.